US8270508B2 - Apparatus and method for communication in variable bands - Google Patents

Apparatus and method for communication in variable bands Download PDF

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Publication number
US8270508B2
US8270508B2 US12/332,856 US33285608A US8270508B2 US 8270508 B2 US8270508 B2 US 8270508B2 US 33285608 A US33285608 A US 33285608A US 8270508 B2 US8270508 B2 US 8270508B2
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subcarriers
data
null
bandwidth
bandwidths
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US12/332,856
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US20090154584A1 (en
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Yoshihisa Kishiyama
Kenichi Higuchi
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NTT Docomo Inc
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NTT Docomo Inc
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Assigned to NTT DOCOMO, INC. reassignment NTT DOCOMO, INC. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: HIGUCHI, KENICHI, KISHIYAMA, YOSHIHISA
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/003—Arrangements for allocating sub-channels of the transmission path
    • H04L5/0037—Inter-user or inter-terminal allocation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2626—Arrangements specific to the transmitter only
    • H04L27/2627—Modulators
    • H04L27/2637—Modulators with direct modulation of individual subcarriers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2649—Demodulators
    • H04L27/2653—Demodulators with direct demodulation of individual subcarriers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/0001—Arrangements for dividing the transmission path
    • H04L5/0003—Two-dimensional division
    • H04L5/0005—Time-frequency
    • H04L5/0007—Time-frequency the frequencies being orthogonal, e.g. OFDM(A), DMT
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/003—Arrangements for allocating sub-channels of the transmission path
    • H04L5/0037—Inter-user or inter-terminal allocation
    • H04L5/0039—Frequency-contiguous, i.e. with no allocation of frequencies for one user or terminal between the frequencies allocated to another
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2602—Signal structure

Definitions

  • the present invention generally relates to the technical field of mobile communications, and more particularly relates to apparatuses and methods for communication in variable bands.
  • the Orthogonal Frequency Division Multiplexing (OFDM) scheme has various advantages such as high tolerance for multipath transmission channels and high efficiency of frequency utilization.
  • OFDM Orthogonal Frequency Division Multiplexing
  • data is mapped into a large number of subcarriers arranged orthogonally with each other, and inverse Fourier transform is performed on the mapped data pieces to derive a time-series signal and generate transmitted symbols for radio transmission.
  • Fourier transform is performed on the symbols to derive the transmitted data pieces, and the individual data pieces associated with the respective subcarriers are restored to reconstruct the transmitted data.
  • FIG. 1 shows exemplary signals communicated in the OFDM scheme.
  • Data to be transmitted is mapped into several subcarriers.
  • one of the subcarriers corresponding to a central frequency f 0 is not used for the data mapping and thus is a subcarrier without data.
  • the central frequency corresponds to a carrier frequency, and thus even if data is mapped into it, the data cannot be transmitted with high quality due to a strong interference component caused there.
  • the central frequency may be referred to as “DC subcarrier” or “DC offset”.
  • UE user equipment
  • user apparatuses use a part or full range of the system band depending on conditions.
  • the whole system bandwidth of 20 MHz is provided, and user apparatuses are allowed to use 10 MHz or 20 MHz for communication.
  • a larger number of system bandwidths may be provided.
  • system bandwidths such as 1.25 MHz or 2.5 MHz may be provided.
  • Utilization efficiency of radio resources may be improved through selection of suitable bands among various bands with greater and smaller bandwidths depending on communication environments and applications.
  • 3GPP TR25.814 V1.5.0 discloses communication systems for communication in variable bands.
  • the communications in variable bands used herein does not mean that user apparatuses are allowed to use the whole frequency in the bands.
  • one or more of resource blocks included in a variable band assigned to a user apparatus are available for communication.
  • the inventors had an idea that the communication in variable bands may be achieved in the OFDM scheme. If the idea can be realized, the above-mentioned outstanding advantages of the OFDM scheme, such as high tolerance over multipath interference and high efficiency of frequency utilization, can be applied to the communication in various bands, which may improve transmission efficiency. Also in this case, it must be taken into consideration the central frequency of a band used in communication should not be used for data transmission.
  • FIG. 3 shows exemplary communications in variable bands in connection with FIG. 2 .
  • the relationship between subcarriers and central frequencies is clarified.
  • users A and D communicate with the bandwidths of 10 MHz and 20 MHz, respectively, and the respective central frequencies are the same frequency f 0 .
  • data can be transmitted with subcarriers other than the central frequency f 0 as is the case of conventional systems in accordance with the OFDM scheme.
  • users B and C use 10 MHz similar to user A but have central frequencies different from user A.
  • the central frequency (DC subcarrier) of a band with 10 MHz for user B is denoted by “f B ” while the central frequency of a band with 10 MHz for user C is denoted by “f C ”.
  • f B the central frequency of a band with 10 MHz for user B
  • f C the central frequency of a band with 10 MHz for user C
  • no data can be mapped into the frequency f B in communications with user B.
  • no data can be mapped into the frequency f C in communications with user C.
  • the frequencies f B and f C do not correspond to the DC subcarrier and accordingly are available for data transmission.
  • the frequency f B or f C can or cannot be used for the data mapping depending on the bandwidth for user apparatuses.
  • frequency scheduling has to be performed by determining availability of individual subcarriers for the data mapping, which may not be desirable from the viewpoint of increasing the complexity of controlling base stations.
  • One object of the present invention is to transmit signals in various bands in OFDM based communication systems with high quality in a simplified manner.
  • an embodiment of the present invention relates to a transmitter for OFDM based communication in a bandwidth selected among multiple bandwidths provided for a system, comprising: a mapping unit configured to convert transmitted data into data pieces associated with individual subcarriers; an inverse Fourier transform unit configured to convert the data pieces into a time-series signal; and a symbol generation unit configured to generate symbols for radio transmission from the time-series signal, wherein the mapping unit associates the transmitted data with subcarriers different from predefined multiple subcarriers arranged at even intervals on a frequency axis.
  • a receiver for OFDM based communication in a bandwidth selected among multiple bandwidths provided for a system comprising: a Fourier transform unit configured to convert a wirelessly received time-series signal into data pieces in frequency domains; a demapping unit configured to associate the data-pieces with individual subcarriers as data for restoration; and a data restoring unit configured to restore transmitted data from the data for restoration, wherein the demapping unit supplies data comprising the data pieces associated with subcarriers different from predefined multiple subcarriers arranged at even intervals on a frequency axis as the data for restoration.
  • signals can be transmitted in various bands in OFDM based communication systems with high quality in a simplified manner.
  • FIG. 1 shows an exemplary communication scheme in accordance with the OFDM scheme
  • FIG. 2 shows an exemplary communication scheme in various bands
  • FIG. 3 shows another exemplary communication scheme in various bands
  • FIG. 4 is a functional block diagram of a transmitter according to one embodiment of the present invention.
  • FIG. 5 is a functional block diagram of a receiver according to one embodiment of the present invention.
  • FIG. 6 shows an exemplary operation according to one embodiment of the present invention.
  • data to be transmitted is associated with subcarriers different from predetermined multiple subcarriers (null subcarriers) arranged at even intervals on the frequency axis.
  • the data associated with the subcarriers other than the null subcarriers is processed as restored data.
  • the null subcarriers are not used for communications with any user apparatus. Thus, it is not necessary to determine availability of individual subcarriers for the data mapping, which result in simplified control of a base station and improved quality of data transmission without the use of all user apparatuses.
  • the mapping may be performed in accordance with bandwidth information indicative of a relationship between the null subcarriers and variable bandwidths provided in the system.
  • the bandwidth information may be stored in a memory device in advance.
  • FIG. 4 is a functional block diagram of a transmitter according to one embodiment of the present invention.
  • the transmitter may be provided in a base station or a user apparatus.
  • the transmitter as illustrated in FIG. 4 is provided in both a base station and a user apparatus.
  • a serial to parallel (S/P) conversion unit 42 a mapping unit 44 , an inverse fast Fourier transform (IFFT) unit 46 , a guard interval appending (+GI) unit 48 and a radio frequency (RF) unit 50 are illustrated.
  • S/P serial to parallel
  • mapping unit 44 a mapping unit 44
  • IFFT inverse fast Fourier transform
  • GI guard interval appending (+GI) unit 48
  • RF radio frequency
  • the serial to parallel (S/P) conversion unit 42 serves as a serial to parallel conversion unit for converting a sequence of transmitted data into multiple parallel data sequences. In this embodiment, some operations such as channel encoding and data modulation have been performed on transmitted data.
  • the mapping unit 44 associates the serial to parallel converted data pieces with individual subcarriers in accordance with bandwidth information. For example, predetermined multiple subcarriers are uniquely associated with individual bandwidths such as 20 MHz, 10 MHz or 5 MHz. These subcarriers are referred to as “null subcarriers” and are not used for data mapping.
  • the bandwidth information indicates which bandwidth is available to the transmitter for communication and which subcarrier is associated with the null subcarrier in the bandwidth.
  • the mapping unit 44 associates the parallel data pieces with subcarriers other than the null subcarriers.
  • the mapping is also subject to information indicating which data pieces are multiplexed to which resource blocks in what manner. For clarification, however, detailed descriptions of such multiplexing and scheduling are omitted.
  • the inverse fast Fourier transform (IFFT) unit 46 performs inverse fast Fourier transform on the data pieces associated with the individual subcarriers for OFDM based modulation.
  • the guard interval appending (+GI) unit 48 appends a guard interval to the modulated time-series signal.
  • the radio frequency (RF) unit 50 converts the guard interval appended signal into transmitted symbols for radio transmission from an antenna.
  • the radio frequency unit 50 performs some operations such as band limitation and frequency conversion.
  • a carrier wave is adapted to the central frequency of a band used by the transmitter. Specifically, if the transmitter is provided in a base station or a user apparatus that uses the whole system band, the carrier wave is set to the central frequency f 0 of the system band. On the other hand, if the transmitter is provided in a user apparatus that uses a part of the system band, the carrier wave is set to any null carrier f B , f 0 or f C .
  • FIG. 5 is a functional block diagram of a receiver according to one embodiment of the present invention.
  • a radio frequency (RF) unit 52 a radio frequency (RF) unit 52 , a guard interval removal ( ⁇ GI) unit 54 , a fast Fourier transform (FFT) unit 56 , a demapping unit 58 and a parallel to serial conversion (P/S) unit 60 are illustrated.
  • RF radio frequency
  • ⁇ GI guard interval removal
  • FFT fast Fourier transform
  • demapping unit 58 a parallel to serial conversion
  • P/S parallel to serial conversion
  • the radio frequency (RF) unit 52 converts the symbols received via the antenna into a signal for processing in a baseband.
  • the radio frequency unit 52 performs some operations such as band limitation and frequency conversion.
  • the carrier wave is adapted to the central frequency of a band used by the receiver.
  • the guard interval removal ( ⁇ GI) unit 54 removes a portion of the received signal corresponding to a guard interval.
  • the fast Fourier transform (FFT) unit 56 performs fast Fourier transform on guard interval removed symbols (effective symbols) for OFDM based demodulation. As a result, data pieces mapped into subcarriers can be derived.
  • FFT fast Fourier transform
  • the demapping unit 58 extracts and generates data mapped into the subcarriers other than the null subcarrier from the derived data pieces.
  • the null subcarrier can be determined based on the bandwidth information.
  • the parallel to serial (P/S) conversion unit 60 serves as a parallel to serial conversion unit for converting the (parallel) data pieces mapped into the subcarriers other than the null subcarrier into a data sequence.
  • the converted data is subject to subsequent operations for restoring the transmitted data.
  • transmitted data is supplied to the S/P unit 42 in FIG. 4 for conversion into multiple parallel data pieces, which are supplied to the mapping unit 44 .
  • the mapping unit 44 associates the parallel data pieces with subcarriers other than the null subcarrier. No data is mapped into the null subcarrier.
  • an odd number of the null subcarriers are provided in a single system band.
  • the null subcarriers are arranged at even intervals on the frequency axis.
  • one null subcarrier is provided every six subcarriers.
  • the central null subcarrier in the odd number of null subcarriers corresponds to a carrier wave in radio communication by a user apparatus.
  • the central null subcarrier f 0 corresponds to a DC subcarrier for a band in accordance with the conventional OFDM scheme.
  • information indicating the relationship between a certain subcarrier and a null subcarrier for that subcarrier is fixed in a memory device of the user apparatus and is extracted as bandwidth information as needed.
  • the preset number of null subcarriers and the interval between the null subcarriers are determined depending on the type of variable bands available to the system.
  • the interval between the null subcarriers is set to be half of the bandwidth available to any user apparatus, that is, the bandwidth at least guaranteed for any user apparatus, and is equal to 10 MHz in the illustrated case.
  • the mapping unit 44 in FIG. 4 maps data into subcarriers other than the null subcarriers and supplies the resulting data pieces to the IFFT unit 46 .
  • “0”s are illustrated at positions corresponding to the null subcarriers.
  • the three “0”s correspond to f B , f 0 and f C in FIG. 6 .
  • the data pieces mapped into the subcarriers other than the null subcarriers are fast Fourier transformed. Then, a guard interval is appended to the transformed signal, and the finally resulting symbols are transmitted from an antenna over the air.
  • the receiver Upon receiving the transmitted symbols, the receiver removes the guard interval and performs Fourier transform on the resulting signal.
  • the demapping unit 58 in FIG. 5 determines the subcarriers other than the null subcarriers for the converted data pieces and extracts the data pieces mapped into the individual subcarriers. Similar to the transmitter side, information indicative of the relationship between the used band and the null subcarriers is derived from the bandwidth information.
  • the individual data pieces are converted by the P/S conversion unit 60 into a signal sequence for restoring the transmitted data subsequently.
  • the null subcarriers preset in the system are not used for communications with any user apparatus.
  • the availability of individual subcarriers for data mapping does not have to be determined, which can simplify the control of a base station and improve the quality of data transmission without use of the DC subcarrier.

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Mobile Radio Communication Systems (AREA)
  • Transmitters (AREA)
US12/332,856 2006-06-19 2008-12-11 Apparatus and method for communication in variable bands Expired - Fee Related US8270508B2 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
JP2006-169450 2006-06-19
JP2006169450A JP4954617B2 (ja) 2006-06-19 2006-06-19 可変帯域で通信するための装置及び方法
PCT/JP2007/061932 WO2007148584A1 (ja) 2006-06-19 2007-06-13 可変帯域で通信するための装置及び方法

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PCT/JP2007/061932 Continuation WO2007148584A1 (ja) 2006-06-19 2007-06-13 可変帯域で通信するための装置及び方法

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EP (1) EP2037609A4 (de)
JP (1) JP4954617B2 (de)
KR (1) KR20090019867A (de)
CN (1) CN101507158A (de)
BR (1) BRPI0713284A2 (de)
RU (1) RU2008151381A (de)
TW (1) TW200820656A (de)
WO (1) WO2007148584A1 (de)

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JP5168015B2 (ja) * 2008-07-31 2013-03-21 富士通モバイルコミュニケーションズ株式会社 無線基地局装置および移動無線端末装置
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JP5912025B2 (ja) * 2011-10-20 2016-04-27 株式会社メガチップス 通信装置および通信システム
GB2506418A (en) * 2012-09-28 2014-04-02 Sony Corp A base station allocates a centre frequency for an OFDM virtual channel in dependence upon a terminal's bandwidth capability
CN105577337A (zh) * 2014-10-17 2016-05-11 中兴通讯股份有限公司 一种下行信号的发送、接收方法及装置
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US10524255B2 (en) 2016-05-20 2019-12-31 Lg Electronics Inc. Method and apparatus for handling DC subcarrier in NR carrier in wireless communication system
WO2018021676A1 (en) * 2016-07-27 2018-02-01 Lg Electronics Inc. Method and apparatus for handling dc subcarrier in nr carrier in wireless communication system
KR101978247B1 (ko) 2017-11-27 2019-05-14 현대오트론 주식회사 풀 스로틀 시 변속시점 제어방법 및 이를 통해 제어되는 변속기
KR102528624B1 (ko) 2019-04-12 2023-05-04 삼성전자 주식회사 무선 통신 시스템에서 로컬 주파수를 결정하는 방법 및 장치
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US20090154584A1 (en) 2009-06-18
RU2008151381A (ru) 2010-07-27
KR20090019867A (ko) 2009-02-25
EP2037609A4 (de) 2014-03-19
JP4954617B2 (ja) 2012-06-20
TW200820656A (en) 2008-05-01
EP2037609A1 (de) 2009-03-18
JP2007336497A (ja) 2007-12-27
BRPI0713284A2 (pt) 2012-03-06
CN101507158A (zh) 2009-08-12
WO2007148584A1 (ja) 2007-12-27

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